Catalytic converter / exhaust system

[SebW20]

I've been running my current Rev 5 NA with a de-cat & mongoose exhaust since I bought it but have recently switched to standard OEM cat and exhaust, the only other mod is a pipercross panel filter. I've been surprised with how noticeable the power-loss is having switched back to the stock system, especially in the last 1000rpms.

I've run other cars with & without cats and it's always been debatable whether you can feel a difference but I'm pretty sure with this one!

I'd be interested to hear other people's experiences or know if anyone's done any dyno runs to see on paper what kind of difference is made?

[Draven]

There is always going to be an increase in power on a car without a cat especially a turbo charged car, a cat will limit flow and that flow is required to spool the turbo.

Not quite so noticeable with an N/A (in standard guise)